Recently, according to increased usage of vehicles and increased traffic volume, air pollution due to exhaust gas comes to the fore as a serious social problem.
Therefore, governments of every country set an emission standard of pollutant in exhaust gas such as carbon monoxide (CO), hydrocarbon (HC), nitrogen oxide (NOx), and the like, in order to regulate exhaust gas. Regulations on the exhaust gas are becoming more and more strict.
Also, manufacturers of vehicles make a great efforts to effectively cope with the regulations on the exhaust gas as the regulations become more strict. An embodiment vehicle may be manufactured in accordance with an exhaust gas emission standard.
Particularly, in order to satisfy an exhaust gas emission standard, a three way catalyst converter in which a noble metal is immersed is mounted in an exhaust system of the vehicle to accelerate decomposition of hydrocarbon, oxidation of carbon monoxide, and reduction of nitrogen oxide.
Also, a gasoline vehicle conducts fuel-cut which cuts fuel injection during decrease in speed to improve fuel consumption. After finishing the fuel-cut, the three way catalyst is saturated with oxygen, so an oxygen (O2) purge is conducted to eliminate the oxygen existing on the three way catalyst.
However, the three catalyst may not temporarily reduce NOx during the O2 purge, and exhausts the flowing NOx, as it is. In other words, the exhaust gas is in a rich state during O2 purge, but the three way catalyst itself is in a lean state (oxidizing atmosphere) due to stored oxygen during fuel-cut, because oxygen storage capacity (OSC) exists in the three way catalyst. Therefore, performance of reduction in NOx is deteriorated, and the performance of the catalyst deteriorates.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.